Röntgenographische und elektrische Untersuchungen bestrahlungsinduzierter Punktdefekte in Si, Ge und ZnSe

Single-crystals ofSi, Ge and ZnSe have been irradiated with 2.5 MeV electrons at 4 Kor at 330 K. The irradiation induced defects and their thermally activated reactions have been investigated by measurements of the diffuse X-ray scattering elose to the Bragg reflections, of the change of the lattice parameter and of the electrical properties. For Si the diffuse X-ray scattering shows that a high concentration of defects (> 10$^{19}$ cm$^{-3}$) can be frozen in at 4 K. A large faction of the defects is stabilized in the form of close Frenkel pairs which are characterized by the nearly perfect cancellation of the long range displacement fields of the interstitial atom and the vacancy. We discuss the absolute size of these displacements as well as the introduction rate of the defects, which is of the order of $\Sigma$ = 1 cm$^{-1}$. Similar results are obtained for weakly doped Cz-Si or FZ-Si and for degenerate p-type Si(B) and n-type Si(As), i.e. the results are independent of the oxygen content of the samples and of the position of the Fermi level. The high defect introduction rates are at variance to the results of electrical and EPR investigations and we discuss the consequences for the understanding of the defect production in Si and for the assumption of an athermal migration of interstitial atoms. In addition we discuss the thennally activated defect reactions up to the final annealing at 1000 K. The results for Ge show remarkable similarities to those of Si. A large number of close Frenkel pairs can be produced ($\Sigma$ = 3 cm$^{-1}$ ) without indication of saturation up to a dose of 3 x 10$^{19}$ cm$^{-2}$. Final annealing is observed at 500 K. The first results on Frenkel defects in the lI-VI compound ZnSe yield an average introduction rate in the order of $\Sigma$ = 3 cm$^{-1}$ for both sublattices. In contrast to the observations with the elemental semiconductors there is an increase of the lattice parameter with irradiation dose which indicates, that there is no complete cancellation between the displacement fields due to vacancies (V$^{rel}_{v}$ = -0.25 atomic volumes) and interstitial atoms (V$^{rel}_{i}$ 0.4 atomic volumes). Two weIl defined low temperature annealing stages are observed which are located between 20 K and 50 K and between 100 K and 220 K, respectively. Only the second stage has been observed so far and has been attributed to the recombination of close Frenkel pairs on the Zn-sublattice. Hence, the low temperature stage yields the first evidence for Frenkel pairs on the Sn-sublattice. Final annealing is observed at 650 K